Lubricating compositions containing salts of monocarboxylic acids and free alkalinity



March 29, 1960 A. J. MORWAY ET AL 2,930,757

LUBRICATING COMPOSITIONS CONTAINING SALTS 0F MONOCARBOXYLIC ACIDS ANDFREE ALKALINITY Filed Oct. 16, 1957 Eiv 1) l.

VISCOSITY AT IOOF. OF FINISHED LUBRICANTS S r M n e V .m

r J .IM W W o.mo Mm S d M' u mum AHH By 56 a M Attorney United StatesPatent Arnold J. Morway, Clark, N.J., and Henry F. Lipiuski and Hugh T.Shearer, Jr., Pittsburgh, Pa., assiguors to Esso Research andEngineering Company, a corporation of Delaware Application October 16,1957, Serial No. 690,561

9 Claims. (Cl. 25240.7)

This invention relates to new and useful lubricant thick-- enerconcentrates, to lubricating compositions containing the thickenerconcentrates and to their methods of preparation. More particularly, theinvention pertains to improvements in the manufacture of lubricating oildispersed mixtures of metal salts of low molecular weight monocarboxylicacids and moderate molecular weight monocarboxylic acids and to finishedlubricants containing them.

It is known to prepare anhydrous lubricating oil thickener concentratescomprising lubricating oil dispersions of mixtures of metal salts of lowmolecular weight monocarboxylic acids having from 1 to 3 carbon atomsper molecule and metal salts of moderate molecular weight monocarboxylicacids having from about 7 to 10 carbon atoms per molecule. The knownprocess comprises coneutralizing low molecular weight and moderatemolecular weight monocarboxylic acids with a metal base in a lubricatingoil menstruum at temperatures in the'range of about 250 to 350 F. toform a lubricating oil thickener concentrate. The lubricating oilthickener concentrate is then dispersed at temperatures in the range ofabout 80 to 350 F. in additional lubricating oil to form finishedlubricants having outstanding extreme pressure properties, detergencyproperties, and other desirable lubricant characteristics. In this knownprocess no attempt'is made to control the free alkalinity of thelubricating oil thickener concentrates other than to approachstoichiometric proportions. It has now been found that products preparedwithout controlling the free alkalinity of the thickener concentratesresults in products of varying and uncertain viscosity. It is desirablethat the finished lubricants have as low a viscosity at 100 F. aspossible for ease of pumping and dispensing though mechanicaldispensers. However, a lowering in viscosity must not take place bydecreasing the mixed salt content of the finished lubricants since themixed salts impart the detergency and wear reducing properties.

The present invention is based on the surprising discovery that anincrease in the free alkalinity of thickener concentrates of the abovetype to between 1% and 1.8 wt. percent, expressed as sodium hydroxide,and based on the weight of the thickener concentrate, materially lowersthe viscosity of the finished lubricants to provide ease of handling anddispensing without necessitating any lowering of the mixed salt content.Moreover, the neutralization potentials of the finished lubricants areincreased without aflecting their stability or anti-wear properties.This is an important factor where residual fuels of high sulfur contentare employed inan engine in conjunction with the lubricants because thefree alkalinity of the lubricants helps to neutralize sulfuric acidformed therein under combustion conditions.

Accordingly, a feature of the present invention is that lubricating oilthickener concentrates comprising a high alkalinity lubricating oildispersion of a mixture of metal salts of low molecular weightmonocarboxylic acids and metal salts of 'moderate molecular weightmonocarboxylic "ice 2 acids can be prepared. which are useful forpreparing finished lubricants of controlled viscosity. t

Another feature of the present invention is that finished lubricants canbe prepared by dispersing the above thickener concentrates in additionallubricating oil.

The high alkalinity lubricating oil thickener concentrates of thepresent invention can vbe prepared by coneutralizing low molecularweight and moderate molecular weight monocarboxylic acids in alubricating oil medium at elevated temperatures with a quantity of metalbase sufiicient to produce thickeners having a free 'alka-, linity inthe range of about 1 to 1.8 wt. percent, based on the weight of thethickener. However, it is not necessary to co-neutralize the acids in alubricating oil medium. A portion or all of the metal salt of either orboth of the acids can be preformed under substantially dehydrationconditions. Thereafter the salts and any required free monocarboxylicacids and metal base are mixed with the lubricating oil and theresulting mixture heated to a temperature in the range of 250 to 350 F.

The figure is a plot of the free alkalinity of thickener concentratesprepared in accordance with the invention against the viscosity offinished lubricants prepared from the thickener concentrates inaccordance withcthe invention.

The low molecular weight acids used to form components of the saltmixtures are saturated and unsaturated monocarboxylic acids having from1 to 3 carbon atoms, such as formic, acetic, propionic, acrylic, andlactic acids. Acetic acid is especially preferred. Mixedlow molecularweight carboxylic acids wherein the acids contain from about 1 to 3carbon atoms and have an average saponification value of above about 540can also be employed.

The moderate molecular weight acids used to form a component of the saltmixtures are those aliphatic monocarboxylic acids containing from about7 to 12. carbon atoms. Especially preferred are the low molecular weightcoconut acids, which are a mixture of acids having from 8 to 12ccarbonatoms, averaging about 10 carbon atoms per molecule. 7 Either saturatedorunsaturated acids can be utilized, although the saturated acids arepreferred. Straight chain or substantially straight chain acids are alsopreferred. The average saponification value of the moderate molecularweight carboxylic acids should be about 310 to 440, preferably about 320to, 350. Some" of the moderate molecular weight monocarboxylic acidscoming within the above description are the following:

5-methyl-2-hexanoic Heptanoic (enanthic) Octanoic (cap'rylic) 2-ethyl'hexanoic C branched chain acids Nonanoic (pelargonic) Decanoic (capric)C branched chain acids Commercial mixtures of moderate molecular weightcarboxylic acids having an average saponification value of from about310 to 400 can also be employed, such as those made by the 0x0 process,described in US. Patents No. 2,632,921; 2,537,577; and 2,553,364.

The thickener concentrates are formed by reacting from about 10 to 25wt. percent, preferably 12 to 20 wt. percent of low molecular weightmonocarboxylic acidspfrom about 1 .to 6 wt. percent, preferably 2 to 5wt. percent of moderate molecular weight monocarboxylic acids, and fromabout 5 to 20 wt. percent, preferably 8 .to 15 wt. percentof a rnetalbase in about 50 to wt. percent, preferably 60 to 75 wt. percentlubricating oil. Alternatively, the acids and base can be reacted in 40to 60 wt. percent lubricating oil and from 20 to 15 wt; percentlubricating oil added thereafter to form the thickener concentrates.These thickener concentrates accordingly are composed of about 50 to 75wt. percent, preferably 60 to 75 wt. percent lubricating oil and fromabout 50 to 25 wt. percent, preferably 40 to 25 wt. percent, of amixture of the low and moderate molecular weight acid salts.

The mol ratio of low molecular weight monocarboxylic acids to moderatemolecular weightmonocarboxylic acids forming the mixture of acids is inthe range of 2:1 to 40:1, preferably 5:1 to 15:1.

The temperature at which the thickener concentrates are formed is animportant aspect of the present invention, since the temperature offormation determines the physical and chemical characteristics of theresulting thickener concentrates and the finished lubricants madetherefrom. Temperatures in the range of 250 to 350 F., preferably 300 to320 F. are employed.

The finished lubricants of the invention are prepared by dispersing theabove thickener concentrates in lubricating oil at a temperature in therange of about 80 to 350 F. to give a finished lubricant having fromabout 1 to 15 wt. percent, preferably 3 to 12 wt. percent mixed low andmoderate molecular weight monocarboxylic acid metal salts presenttherein.

The metal bases used to neutralize the monocarboxylic acids are thealkaline earth metal bases or the heavy metal bases of groups I, II, IVand VIII of the periodic system, such as copper, zinc, lead, cobalt,strontium, and magnesium. The alkaline earth metal bases are preferred,and the calcium bases are particularly preferred. Alkali metals are notuseful since lubricants containing them have poor structural stability.

The metal bases used are preferably the metal hydroxides although oxidesand carbonatw can also be used. Two or more metal bases can be used,although in most instances only one metal base is employed.

The choice of lubricating oil used to form the thickener concentratesand the finished lubricants depends on the particular use contemplatedfor the lubricant. A wide variety of mineral as well as syntheticlubricating oils can be used. In general, the lubricating oil shouldhave a viscosity within the range of about 60 to 2500 S.S.U. at 100 F.and about 35 to 200 S.S.U. at 210 F., a pour point of about +20 to -75F., and a flash point of about 350 to 650 F. Oils having a viscosityindex of 100 or higher are usually desirable, though oils having a lowerviscosity index can be employed. As previously mentioned, synthetic aswell as mineral lubricating oils can be employed as part or all of theliquid phase of the grease and they include synthetic lubricating oilsof the hydrocarbon, hydrocarbon polymer, ester, complex ester, formal,mercaptal, polyalkylene oxide, silicone and similar types. Syntheticoils such as the simple diesters can also be used, e.g. di-2-ethylhexylsebacate, di-isooctyl azelate and the complex esters formed from glycolsor alcohols or both with dicarboxylic acids or monocarboxylic acids orboth.

The finished lubricants can also be prepared by dispersing a thickenerconcentrate in a lubricating oil of different viscosity than thelubricating oil used to form the concentrate.

The invention will be understood more fully from the following specificexamples.

EXAMPLE I A lubricating oil thickener concentrate was prepared by mixing1777 lbs. of hydrated lime and 7600 lbs. of a mineral oil of a viscosityof 1200 S.S.U. at 100 F. in an 18,000 lbs. capacity steam-heated doubleaction paddled grease kettle. The components were intimately mixed toform a slurry and to the slurry was charged a blend of 2455 lbs. ofglacial acetic acid and 595 lbs. of coconut acids (a mixture of 26%caprylic acid, 57% capric acid and 17% lauric acid) over a period ofabout 1 hour. After 30 minutes mixing, the temperature had increased toa temperature in the range of 180 to 200 F. External heating was theninitiated and the temperature raised to 320 F. during the course of 4hours. Thereafter, heating was discontinued and the mixture cooled bythe addition of 5000 lbs. of the above mineral oil and by the passage ofcold water through the kettle jacket. The resultant thickener was cooledto 110 F. and passed from the kettle through a Charlotte Mill with a0.003" opening to a storage tank. The free alkalinity of the thickenerconcentrate was 1.14 wt. percent, as shown in Table I.

EXAMPLES H AND III These thickener concentrates were prepared inaccordance with the process of Example I using the formulations given inTable I. The free alkalinities of these thickeners are also given inTable I.

EXAMPLES IV THROUGH VI These thickener concentrates were prepared forcomparison with the thickener concentrates of the invention inaccordance with the process given in Example I except that smallerquantities of lime than those required to yield a thickener concentratehaving a free alkalinity between 1 and 1.8 wt. percent were employed.The free alkalinity of these thickener concentrates likewise are givenin Table I.

1 Examples I, II, and III, are the thickeners 01' the invention. 1 Ablend of approximately 26% coprylic acid, 57% capric acid and 17% lauricacid.

Finished lubricants were prepared from the thickener concentrates ofTable I as shown in the following examples.

EXAMPLE VII The thickener concentrate prepared in Example I was passedthrough a Charlotte Mill a second time to a tank equipped with a sideentrance paddle. 5900 gallons (44,- 840 lbs.) of mineral oil of 1200S.S.U. viscosity at F. was added and the mixture intimately mixed at F.The finished lubricant was then passed through a Cornell homogenizer fordeaeration and then through a Purolator filter having 0.015 spacing. Thelubricant was then inspected and packaged. The inspection data for thelubricant are given in Table II.

EXAMPLES VIII THROUGH XII These lubricants were prepared according toprocess of Example VII using the thickener concentrates of Examples IIthrough VI respectively. Each finished lubricant was prepared by mixingall of the appropriate thickener concentrate with 44,840 lbs. of themineral oil of Example VII. The inspection data for these lubricants arealso given in Table II.

It can be seen from Tables I and II that increasing the free alkalinityof the thickener concentrates produces a fluid lubricant product havinga desirable lower viscosity.

If a lubricant of lower sulfated ash content is desired, such as forexample, not over 5.5 the ash content obtained with a lubricant such aslubricant VI can easily be reduced to 5.5% by the addition of 9% mineraloil having a viscosity of 1200 S.S.U. at 100 F. to obtain a lubricanthaving a viscosity of 1705 S.S.U. at 100 F.

Table 11 [Finished Lubricants Properties X XI XII VII VIII IX ViscosityS.S.U./100 F 2, 150 2, 011 1, 910 l, 893 1, 863 1,852 Four Ball WearScar (Spot diam. mm. 1,800

75 O.-1 hour) 0. 20 0.22 0.21 0. 19 0.22 0.20 Sulfated Ash, Percent- 6.56 5. 62 5. 80 5. 87 5. 97 6.00 Centrifuge Test (4 Hrs. at

1,500 rpm.) l. 8 1. 8 1. 8 1. 1. 8 1. 8 Water by Distillation,

Percent 0. 1 0. 1 O. 1 0. l 0. 1 0. 1 Screen Test (100 mesh).-- Nolumps, gel or unreacted lime specks Dispensing (Manzell).. Satisfactoryon 14 day test 1 Examples VII, VIII and IX are the finished lubricantsof the invention.

It is to be noted that the amount of hydrated lime which is included inthe above formulations to obtain the high alkalinity thickenerconcentrates is not appreciably higher than the amount used to obtainlow alkalinity thickener concentrates. For example, comparing the datafor Examples I and VI given in Table I, it can be seen that an increaseof less than 6% in the amount of added hydrated lime produces anincrease in free alkalinity of over 240%.

The decrease in viscosity of the lubricants produced by increasing thefree alkalinity of the corresponding thickener concentrates is shown inthe figure. In the figure the free alkalinity of the thickenerconcentrates of Table I is plotted against the viscosity of thecorresponding finished lubricants of Table II. It can be seen that anincrease in free alkalinity of from 0.48 to 1.64 produces a marked andsurprising decrease in the viscosity of the lubricant. e

The lubricants prepared in accordance with the inven-'- tion can containvarious conventional additives such as oxidation inhibitors, metaldeactivators, corrosion preventatives, extreme pressure agents, dyes,and'the like as understood by those skilledin the art.

What is claimed is: l

1. A lubricant thickener concentrate which comprises about 50 to 75 wt.percent of a lubricating oil having a viscosity in the range of 60 to2500 S.S.U. at 100- F., and about 25 to 50 wt. percent of a mixture ofalkaline earth metal salts of low molecular weight monocarboxylic acidshaving from 1 to 3 carbon atoms per molecule and alkaline earth metalsalts of moderate molecular weight monocarboxylic acids having from 7 to12 carbon atoms per molecule, the mol ratio of said low to said moderatemolecular weight acids being in the range of 2:1 to 40:1, said thickenerconcentrate having a free alkalinity inthe range of 1 to 1.8 Wt.percent.

2. The lubricant thickener concentrate of claim 1 wherein the mol ratioof low 'to moderate molecule weight acids is in the range of 5:1 to15:1.

3. The lubricant thickener concentrate of claim 1 wherein saidconcentrate is prepared at a temperature in the boxylic acids havingfrom 8 to1 2 carbon atoms per adding suflicient alkaline earth metalbase to the mixture I to obtain a thickener concentrate having a freealkalinity in therrange of 1 to 1.8 wt. percent.

6. The method of preparing a lubricant thickener concentrate having afree alkalinity in the range of 1 to 1.8

wt. percent comprising dispersing 10 to Wt. percent low molecular weightmonocarboxylic acids having from 1 to 3 carbon atoms per molecule, 1 to6 wt. percent moderate molecular weight monocarboxylic acids having from7 to 12 carbon atoms per molecule, and suflicient alkaline earth metalbase to obtain a thickener concentrate having a free alkalinity in therangeoof 1 to 1.8%, in

50 to 75 wt. percent lubricating oil having a viscosity in the range'of60 to 2500 S.S.U. at 100 F., and heating said dispersion to atemperature in the range of 250 to 350 F. to produce said concentrate. vJ 7. The method of preparing a lubricant thickener concentrate having afree alkalinity-in the range of 1 to 1.8

Wt. percent comprising forming a mixture of 12 .to 20 wt. percent lowmolecular weight monocarboxylic acids having from 1 to 3 carbon atomsper molecule, 2 to 5 wt. percent moderate molecular weightmonocarboxylic acids" having from 7 to 12 carbon atoms per molecule,suflicient alkaline earth metal base to obtaina thickener concentratehaving a free alkalinity in the range of 1- to 1.8%, in 60 7 H575 wt.percent lubricating oil' having a viscosity in the range of 60 to 2500S.S.U at 100 F. and heating said mixture to a temperature in the rangeof 250 to 350 F.

to produce said concentrate.

8. The method of preparing a'lubricant thickener .concentrate accordingto claim 7 wherein the low molecular weight monocarboxylic acids areacteic acid, the moderate molecular weight monocarboxylic acids are amixture of monocarboxylic acids having from 8 to 12 carbon atoms permolecule, and the metal base is an alkaline earth metal base.

9. The method of claim 8 wherein the alkaline earth metal base iscalcium hydroxide.

I V I References Cited in the file of this patent UNITED STATES PATENTS2,070,014 Lincoln'et al. Feb. 9, 1931 2,265,791 Zimmer et al. Dec. 9,1941 2,503,969 Rudel et al. Apr. 11, 1950 2,755,256 Dilworth et a1 July17, 1956 2,758,973 Morway etal. Aug. 14, 1956 2,839,470 Warren et al.June 17, 1958 FOREIGN PATENTS 778,651 Great Britain July 10, 1951

1. A LUBRICANT THICKENER CONCENTRATE WHICH COMPRISES ABOUT 50 TO 75 WT.PERCENT OF A LUBRICATING OIL HAVING A VISCOSITY IN THE RANGE OF 60 TO2500 S.S.U. AT 100*F., AND ABOUT 25 TO 50 WT. PERCENT OF A MIXTURE OFALKALINE EARTH METAL SALTS OF LOW MOLECULAR WEIGHT MONOCARBOXYLIC ACIDSHAVING FROM 1 TO 3 CARBON ATOMS PER MOLECULE AND ALKALINE EARTH METALSALTS OF MODERATE MOLECULAR WEIGHT MONOCARBOXYLIC ACIDS HAVING FROM 7 TO12 CARBON ATOMS PER MOLECULE, THE MOL RATIO TO SAID LOW TO SAID MODERATEMOLECULAR WEIGHT ACIDS BEING IN THE RANGE OF 2:1 TO 40:1, SAID THICKENERCONCENTRATE HAVING A FREE ALKALINITY IN THE RANGE OF 1 TO 1.8 WT.PERCENT.